After running my Husky 55 for the past 9 years or so as my only saw until this year, I can say that a 50cc saw will get 'er done on wood up to 30". That is, if you're just cutting for yourself. Been there, got the T shirt.
Now, if you're cutting more than just for yourself, then I think I'd probably go to a 60cc powerhead... more GO than the 50cc, but not quite as heavy.
Now don't get me wrong, I LOVE my 372, but I gotta admit that it is a bit of overkill for a firewood saw. But, I'm not letting go of it anytime soon
My 395 is just a symptom of CAD...
But, for the OP's question in 16" average wood, I'd go with a pro grade 50cc class saw, something like a Husky 357xp or 359 with an 18" bar if I were to be starting over again. And, SEMI-CHISEL chain. The full chisel is great when it's sharp, problem is, it doesn't stay that way very long it seems. I switched over to full chisel when I got the 372, and also put it on the 395. I now kinda wish I would have stayed with the semi-chisel. Over the course of the day, cutting firewood, I'm starting to think it gets more wood cut.